Transplantation of 28 maxillary canines was followed up in 22 patients with an average age of 25.2 s.d. 9.9 years. The root was fully developed. The mean immobilization time was 6.6 weeks and the mean follow-up period 17.8 months. Results seemed to be better in the age group of 13--20 years than in 21--30 and 31--47 years. Statistically significant better results were found in the youngest than in the older groups in the return of vitality, vertical bone resorption, periodontal space in the lamina dura. Four of the 28 teeth were extracted because of great mobility caused by poor bone regeneration and vertical resorption of the alveolar bone: three in the middle age group and one in the oldest. Pulp extirpation was performed on nine teeth: six in the oldest group and three in the middle group. Vitality returned in only three teeth, all of which belonged to the youngest group. Root resorption was observed in all age groups; in 76% of the cases it occurred in the apical third, and was generally inflammatory. The causes of the failure of transplantation were considered to include damage of the transplant during removal from deep palatal malposition, poor regeneration of the bone around the transplant and chronic periodontal infection. The prognosis for transplantation was found to be fairly good for patients under 20 years of age but poorer for older age groups.